A Pakistani official says a rocket attack targeting NATO supply trucks in the country's northwest has killed four people.

Local official Iqbal Khan says the convoy heading to Afghanistan came under attack in the Jamrud area in the Khyber tribal region on Monday.

He says several rockets were lobbed at the convoy and that the four dead were truck drivers and their assistants. Two vehicles were completely burnt.

Khan is a local government official. He says it is not clear who was behind the attack. But the NATO supply line has long been a favorite target of Pakistani Taliban and other militants.

As a result of the attacks, the U.S. has over the years reduced its use of two Pakistani land routes to ferry supplies for soldiers in neighboring Afghanistan.